More particularly, the invention relates to a method for rheological characterization of a viscoelastic medium, comprising the following steps:                (a) an excitation step during which a vibratory excitation with a spectrum that includes at least one nonzero frequency is generated in the viscoelastic medium, said excitation producing a deformation of the medium;        (b) a deformation measurement step during which said deformation of the medium produced by the excitation is observed at a plurality of points in the medium; and        (c) a rheological characterization step during which at least one rheological parameter x of the medium is determined at said plurality of points in the medium from said deformation.        
This thus allows qualitative and/or quantitative analysis, especially for identifying areas of different hardness from the rest of the viscoelastic medium or areas having a different relaxation time from the rest of the viscoelastic medium. One particularly advantageous application of this method is in the imaging of soft tissue in humans, for example for the purpose of detecting cancers.
Document WO-A-04/21038 describes an example of such a method.
Although this method has already given satisfaction, the object of the present invention is to further perfect methods of this type so as to improve the reliability and detection sensitivity thereof.